Duplicate ID Finder

WHAT IT DOES

Duplicate ID Finder is a browser extension that scans any webpage for duplicate ID attributes on elements and lists them with their count. It shows which IDs are duplicated and how many times, and highlights all elements with duplicate IDs using a red outline and label. You can click on any duplicate ID to see a list of all elements that share that ID, and click any element in the list to scroll to it on the page. The tool helps developers identify and fix duplicate ID issues that can break JavaScript functionality, CSS styling, and accessibility. It is ideal for web developers, QA engineers, accessibility testers, and anyone who wants to ensure HTML validity.

WHERE IT RUNS

Duplicate ID Finder runs on any webpage, overlaying a floating panel that does not interfere with page content. It operates entirely in your browser as a lightweight userscript, scanning the DOM for ID attributes. It works on any page, whether static or dynamic, with no external dependencies. All settings are stored locally using GM_setValue—no data is ever sent to any server.

HOW TO USE

After installation, open the floating panel by clicking the extension icon. The panel shows the current status (Enabled or Disabled) and a toggle button to enable or disable the finder. Click the "Scan" button to scan the page for duplicate IDs. The panel displays the total number of duplicate IDs found and a list of each duplicated ID with its occurrence count. Click any ID to see a list of all elements that use that ID. Click an element in the list to scroll to it and highlight it temporarily. The tool also highlights all elements with duplicate IDs directly on the page with a red outline and a label. Click the "Clear Highlights" button to remove the visual highlights. All settings are saved per website.

REAL MECHANISM — WHY THIS WORKS

Most duplicate ID detection requires manual inspection of the page source or using browser developer tools to search for ID attributes. Duplicate ID Finder uses a DOM-scanning approach that automatically finds all elements with ID attributes and identifies duplicates. The tool queries the page using document.querySelectorAll("[id]") to get all elements with IDs, then iterates through them, counting occurrences of each ID and storing references to the elements. It filters to only IDs that appear more than once. Each duplicate ID is displayed with its count, and when clicked, the tool shows the list of elements with that ID. The highlight feature applies CSS outlines to all elements with duplicate IDs, with a label indicating the duplicate ID. A MutationObserver detects dynamically added elements and rescans automatically. This approach ensures accurate, real-time, and fully private duplicate ID detection without requiring any external services or network access.

THE PANEL

The floating panel is fully draggable and remembers its position per site, snapping to the edges of the viewport when dragged near them. You can collapse the panel to a small icon to minimize screen distraction and expand it back with a single click. The panel is resizable from the bottom-right corner, giving you more space to view the duplicate ID list. Press the Escape key to close the panel instantly. The panel remains open across page navigation within the same domain, maintaining your current view state. All preferences—panel position and enabled state—are saved per domain for a seamless experience.

PLEASE NOTE

Duplicate ID Finder requires the free BotGentz extension to be installed and enabled, as it relies on the cross-extension messaging API provided by BotGentz for DOM access permissions. The tool scans all elements with ID attributes and may include IDs from scripts, templates, or dynamically generated content. The tool does not modify page content; it only reads and displays ID information and applies visual highlights. The highlights are temporary and can be cleared. All settings are stored locally in your browser using GM_setValue. No page content, ID data, or usage information is ever sent to any server. The extension does not read, store, or transmit any personal information. It only scans and displays duplicate ID data at your request.